Re: [PATCH v1 0/2] mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()

[Peter Xu]

On Thu, Dec 22, 2022 at 09:55:09PM +0100, David Hildenbrand wrote:
> Playing with virtio-mem and background snapshots (using uffd-wp) on
> hugetlb in QEMU, I managed to trigger a VM_BUG_ON(). Looking into the
> details, hugetlb_change_protection() seems to not handle uffd-wp correctly
> in all cases.
> 
> Patch #1 fixes my test case. I don't have reproducers for patch #2, as
> it requires running into migration entries.
> 
> I did not yet check in detail yet if !hugetlb code requires similar care.
> 
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> Cc: Peter Xu <peterx@xxxxxxxxxx>
> Cc: Muchun Song <muchun.song@xxxxxxxxx>
> Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> 
> David Hildenbrand (2):
>   mm/hugetlb: fix PTE marker handling in hugetlb_change_protection()
>   mm/hugetlb: fix uffd-wp handling for migration entries in
>     hugetlb_change_protection()

Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>

Thanks, David.

-- 
Peter Xu